Preheat oven to 325 degrees F (160 degrees C).
Season the Beef Short Ribs (7) heavily on all sides with Kosher Salt (to taste) and Ground Black Pepper (to taste).
Combine the Onion (2), Garlic (3 clove), Carrot (2 cup), and Baby Potato (8 ounce) in a large bowl and season with Salt and Pepper (to taste). Set aside until needed.
Heat Light Olive Oil (to taste) in the skillet over medium-high heat. Sear the short ribs on all sides until a nice brown color forms, about 8-10 minutes.
Add the vegetables and toss to combine in the pan-juices. Add the Tomato Paste (2 tablespoon) and cook while distributing the paste. Allow to cook for 1-2 minutes.
Add Beef Stock (3 cup) until the vegetables and short ribs are just about, but not fully, submerged. Add the Fresh Thyme (3 sprig) and Bay Leaf (2). Bring to a boil and boil for 2 minutes.
Carefully cover the skillet with foil and transfer to the oven. Cook for 2 1/2 hours.
Peel back the foil and add in Button Mushroom (8 ounce). Cover and cook for another 30 minutes, or until the beef is incredibly tender.
Serve with a slice of French bread to soak up the juices.